The present invention generally relates to forming a Metal-Insulator-Metal structured capacitor with polysilicon instead of a conventional oxide film as a sacrificial layer material that defines a storage electrode region. During formation, a surface area of a sacrificial layer that defines a storage electrode region is increased by a Metal-stable Poly Silicon (hereinafter, referred to as “MPS”) process which also increases the area of the storage electrode formed on the sacrificial layer to increase capacity of the capacitor in a stable manner.
In a process for forming a capacitor of a semiconductor device, an oxide film is used as a sacrificial layer for forming a storage electrode.
FIGS. 1a through 1e are cross-sectional diagrams illustrating a method for forming a conventional Metal-Insulator-Metal capacitor.
Referring to FIG. 1a, an interlayer insulating film 10 including a storage electrode contact plug 20 is formed over a semiconductor substrate (not shown). Then, an etching barrier film 30 is formed over the interlayer insulating film 10.
Referring to FIG. 1b, a sacrificial oxide film 40 for forming a storage electrode is formed over the etching barrier film 30.
Referring to FIG. 1c, the sacrificial oxide film 40 and the etching barrier film 30 are etched with a photoresist pattern that defines a storage electrode region to form a sacrificial oxide film pattern 45 that defines the storage electrode region and a barrier film pattern 35.
Referring to FIG. 1d, a storage electrode material 50 is formed over the semiconductor substrate including the sacrificial oxide film pattern 45.
Referring to FIG. 1e, a CHEMICAL MECHANICAL POLISHING process is performed to remove the storage electrode material 50 formed over the sacrificial oxide film pattern 45 so that only one contact plug 20 is connected to each separated storage electrode 55.
A dielectric layer is formed over the semiconductor substrate including the storage electrode 55, and then a top electrode layer is formed over the semiconductor substrate to complete a capacitor.
As described above, the method for forming a METAL-INSULATOR-METAL capacitor using a sacrificial oxide film includes increasing the height of the sacrificial oxide film or introducing a new material having a high-k dielectric constant in order to increase the capacity of the capacitor since the area of the capacitor is decreased due to high integration of semiconductor devices.
However, when the sacrificial oxide film becomes higher, the process of etching a storage electrode region becomes unstable, and the storage electrode is collapsed or bridged so that the subsequent process of forming a capacitor is not normally performed. Also, it is difficult to introduce new materials.